N-P-K refers to the ratio of important elements in a fertilizer or soil amendment. N stands for nitrogen, which is responsible for strong stem and foliage growth. P is for phosphorus, which aids in healthy root growth and flower and seed production. K stands for potassium, which is responsible for improving overall health and disease resistance.
"the NPK ratio in this fertiliser is just right; look forward to vigorous growth"
by Pseudononymousness September 25, 2008